HTTP reverse proxy server for streaming and long-polling services

 Pushpin is a reverse proxy server that makes it easy to implement
 WebSocket, HTTP streaming, and HTTP long-polling services. It communicates
 with backend web applications using regular, short-lived HTTP requests
 (GRIP protocol). This allows backend applications to be written in any
 language and use any webserver.
 .
 Additionally, Pushpin does all of this without exposing a proprietary
 protocol to clients. The HTTP/WebSocket content between the client
 and your server is whatever you want it to be. This makes it ideal for
 implementing APIs.
 .
 Pushpin is written in C++. The name means to "pin" (hold) connections
 open for "pushing".